The concept of a medical apparatus for humidifying or otherwise treating a gas from an insufflator during surgery is described in Douglas Ott et al. U.S. Pat. Nos. 5,411,474; 6,068,609 and 7,066,902. Briefly, an insufflation gas is heated and hydrated i.e. conditioned, before the gas is directed into a body cavity through a device such as a trocar. In order to hydrate the insufflation gas a charge of hydration fluid is typically injected into a device where the hydration fluid can humidify the insufflation gas and a heater can bring the insufflation gas to a temperature near body temperature. The conditioned insufflation gas is then sent to a trocar for injection into a body cavity of a patient.
One of the requirements for delivery of insufflation gas to a patient's body cavity is to maintain the proper flow of insufflation gas into the body cavity. Normally, gas flows from a high-pressure gas source, which is remote from the patient, through an insufflation device and finally into a trocar where the gas is injected into the patient's body cavity. Typically, the insufflation gas is stored in high-pressure containers and a pressure regulator reduces the pressure of the gas to a lower pressure. The low pressure gas is typically delivered to the trocar through an insufflation device containing a set of inline end connectors that couple the source of insufflation gas, the pressure regulator, the filter, the heater, or heater and hydrator to trocar to each other. During the insufflation process the insufflation gas, which is conditioned by filtering, heating and or hydrating before delivery flows through a number of inline end connectors, which are typically connected by flexible tubing.
The conditioned gas is then delivered to the patient through a trocar cannula that extends into the body cavity of a patient. It is known that each of these devices and the connectors for each of these devices between the source of high-pressure insufflation gas and the body cavity of the patient generate what has been considered a negligible fluid resistance.
Typically, during a surgical procedure the amount of insufflation gas injected into the body cavity of the patient, the flow rate of the insufflation gas as well as the velocity of the insufflation gas varies over a wide range. To avoid tissue damage in the patient the flow rate of insufflation gas as well as the gas insufflation pressure in the body cavity as well as other conditions of the insufflation gas need to be controlled.